The present invention relates to a gas turbine combined plant which comprises a gas turbine section that has an air cooler, and a steam turbine section that has a waste-heat recovery boiler. More particularly, the invention relates to a gas turbine combined plant which has an improved air cooler that uses water of a waste-heat recovery boiler.
The gas turbine compresses air with an air compressor, sends this air to a combustor, heats and combusts obtained compressed air together with a fuel in the combustor, thereby to produce high-temperature and high-pressure gas. The gas turbine expands the high-temperature and high-pressure gas in a turbine to drive the turbine, and obtains power of a generator.
From a viewpoint of improving the efficiency of the gas turbine, it is necessary to suppress a leakage of the gas in the turbine as far as possible. For this purpose, a clearance between a moving section (a moving blade or the like) and a stationary section (a casing that covers the moving blade from an external periphery side) is designed as small as possible.
On the other hand, from a viewpoint of increasing the thermal efficiency of the gas turbine, the operation gas temperature is set to a high level. In order to secure the clearance at this high temperature, it is important to suppress thermal expansion by effectively cooling members of the turbine that become at a high temperature (hereinafter, referred to as a high-temperature members).
For this purpose, the gas turbine is provided with an air cooler that cools the high-temperature air obtained by extracting this air from the air compressor, and supplies this cooled air for cooling the high-temperature members.
Further, in order to effectively utilize the waste heat of an exhaust gas exhausted from the gas turbine, a gas turbine combined plant is put to practical use. This gas turbine combined plant sends this exhaust gas to a waste-heat recovery boiler, drives a steam turbine by using steam obtained from the waste-heat recovery boiler, and obtains power for other generators.
This gas turbine combined plant condenses the steam exhausted by driving the steam turbine with a condenser, and supplies obtained water to the waste-heat recovery boiler. The exhaust gas from the gas turbine section is radiated by passing through a superheater, an evaporator, and an economizer in this order, within the waste-heat recovery boiler. In the mean time, water supplied from the condenser flows through the economizer, the evaporator, and the superheater in this order, thereby to absorb the heat. The waste heat from the gas turbine section is effectively utilized in this way.
Further, a cooling water passage is provided such that a part of the water to the waste-heat recovery boiler is returned to a process as explained below. That is, the part of the water to the waste-heat recovery boiler is guided into the air cooler as a cooling medium that cools the high-temperature air that has been guided to the air cooler of the gas turbine section. The water that has become at a high temperature after heat exchanging with the high-temperature air is returned to the process in which the water of the waste-heat recovery boiler has a higher temperature. In this way, a structure for efficiently carrying out the heat recovery is provided.
According to the above gas turbine combined plant, a pressure of a process (for example, a drum) that leads to a secondary side of the cooling water passage (a side at which water returns from the air cooler to the waste-heat recovery boiler) becomes high, at a starting time of the steam turbine or at a load disconnection time. Therefore, a relative pressure difference between a primary side (a side at which water is guided from the waste-heat recovery boiler to the air cooler) and the secondary side of the cooling water passage becomes small. As a result, a quantity of the water that flows through the air cooler is reduced, and there is a risk that the cooling of high-temperature air may become insufficient.
It is an object of this invention to obtain a gas turbine combined plant which can stably cool high-temperature air of a gas turbine, in various kinds of operation status like a steam turbine starting time and a load disconnection time other than a normal operation time.
The gas turbine combined plant according to one aspect of this invention comprises a gas turbine section and a steam turbine section. The gas turbine section includes an air compressor, a combustor, a gas turbine, and an air cooler that cools high-temperature air obtained by being extracted from the air compressor and supplies cooled air for cooling high-temperature members in the gas turbine. The steam turbine section includes a waste-heat recovery boiler that generates steam based on waste heat of an exhaust gas exhausted from the gas turbine, a steam turbine that is driven by the steam, and a condenser that condenses steam exhausted from the steam turbine into water and supplies the water to the waste-heat recovery boiler. The gas turbine combined plant also comprises a cooling water passage that guides a part of the water from the waste-heat recovery boiler into the air cooler, allows heat-exchange between the water and the high-temperature air, and returns the water after this heat exchange to the waste-heat recovery boiler. The gas turbine combined plant further comprises a branch passage that guides the water after the heat exchange to the condenser, and a regulating valve that regulates a quantity of the water that flows through the branch passage.
The gas turbine combined plant according to another aspect of this invention comprises a gas turbine section and a steam turbine section. The gas turbine section includes an air compressor, a combustor, a gas turbine, and an air cooler that cools high-temperature air obtained by being extracted from the air compressor and supplies cooled air for cooling high-temperature members in the gas turbine. The steam turbine section which includes a waste-heat recovery boiler that generates steam based on waste heat of an exhaust gas exhausted from the gas turbine, a steam turbine that is driven by the steam, and a condenser that condenses steam exhausted from the steam turbine into water and supplies the water to the waste-heat recovery boiler. The gas turbine combined plant also comprises a cooling water passage that guides a part of the water from the waste-heat recovery boiler into the air cooler, allows heat-exchange between the water and the high-temperature air, and returns the water to the waste-heat recovery boiler. The gas turbine combined plant further comprises a bypass passage that guides water at a lower temperature than that of water at a primary side of the cooling water passage into the air cooler, and a switching valve that selectively switches between the primary side of the cooling water passage and the bypass passage.
Other objects and features of this invention will become apparent from the following description with reference to the accompanying drawings.